A set of straight and gleaming
teeth makes for a beautiful smile. But how many people who have undergone a
little dental maintenance know that they may have inside their mouths some of
the first products of a new industrial revolution? Tens of millions of dental
crowns, bridges and orthodontic braces have now been produced with the help of
additive manufacturing, popularly known as 3D printing. Forget the idea of
hobbyists printing off small plastic trinkets at home. Industrial 3D printers,
which can cost up to $1m, are changing manufacturing.

The business of dentures shows how.
For the metal bits in false teeth, dentists have long relied upon a process
called “investment casting”. This involves creating an individual model of a
person’s tooth, often in wax, enclosing it in a ceramic casing, melting out the
wax and then pouring molten metal into the cavity left behind. When the cast is
split open, the new metal tooth is removed. It is fiddly, labour-intensive and
not always accurate; then again, the casting method is some 5,000 years old.

Things are done differently at an
industrial unit in Miskin, near Cardiff, set up by Renishaw, a British
engineering company. The plant is equipped with three of the firm’s 3D printers;
more will be added soon. Each machine produces a batch of more than 200 dental
crowns and bridges from digital scans of patients’ teeth. The machines use a
laser to steadily melt successive layers of a cobalt-chrome alloy powder into
the required shapes. The process is a bit like watching paint dry – it can take
eight to ten hours – but the printers run unattended and make each individual
tooth to a design that is unique to every patient. Once complete, the parts are
shipped to dental laboratories all over Europe where craftsmen add a layer of
porcelain. Some researchers are now working on 3D printing the porcelain, too.

The mouth is not the only bodily
testing-ground for 3D-printed products. Figures gleaned by Tim Caffrey of Wohlers
Associates, an American consultancy that tracks additive manufacturing, show
that more than 60m custom-shaped hearing-aid shells and earmoulds have been
made with 3D printers since 2000. Hundreds of thousands of people have been
fitted with 3D-printed orthopaedic implants, from hip-replacement joints to
titanium jawbones, as well as various prosthetics. An untold number have
benefited from more accurate surgery carried out using 3D-printed surgical
guides; around 100,000 knee replacements are now performed this way every year.

That the health-care industry has
so swiftly adopted additive manufacturing should be no surprise. People come in
all shapes and sizes, so the ability of a 3D printer to offer customised
production is a boon. The machines run on computer-aided design (CAD) software,
which instructs a printer to build up objects from successive layers of
material; a medical scan in effect functions as your CAD file. And software is
faster and cheaper to change than tools used in a traditional factory, which is
designed to churn out identical products.

Compared with the $70 billion
machine-tool market, additive manufacturing is still tiny. But it is expanding
rapidly, and not just in health care. Overall, Wohlers estimates that
3D-printed products and services grew by 26% last year, to be worth nearly $5.2
billion. That is just the tip of a bigger mountain in the making. McKinsey, a
management consultancy, reckons that in terms of things like better products,
lower prices and improved health, 3D printing could have an economic impact of
up to $550 billion a year by 2025.

One reason why 3D printers are
becoming more mainstream is that the “inks” they use are getting better thanks
to advances in materials science, says Andy Middleton, the European head of
Stratasys, an Israeli-American company that makes 3D printers. One method
Stratasys uses, called PolyJet, is similar to inkjet printing: cartridges
deposit layers of a liquid polymer which are cured with ultraviolet light. The
company has just unveiled a new PolyJet model called the J750. It uses multiple
cartridges to print items in 360,000 different colours and any combination of
six different materials, which can be rigid or flexible, opaque or transparent.

The machine is intended to make
prototypes as the polymers are not yet robust enough for a final product.
Nevertheless, that allows a manufacturer of trainers, for instance, to print a
complete shoe in one go, with a rubbery sole and a leather-like upper. The
ability to make realistic prototypes greatly speeds up product approval and the
time it takes to get to market.

Increasingly, however, 3D-printed
objects are being produced as finished items, rather than as models or
prototypes. This leads consultants at PWC to conclude in a new report that
additive manufacturing “is crossing from a period of hype and experimentation
into one of rapid maturation”. Their research found more than two-thirds of
American manufacturers are now using 3D printing in some form or the other.

Another 3D-printing process used by
Stratasys builds parts layer by layer, by heating and extruding thermoplastic
filaments. Airbus now uses these machines to print internal cabin fittings for
its new A350 XWB airliner. The printers use a resin that meets the safety
standards on aircraft. As airlines often specify custom fittings, 3D printing
saves on re-tooling. It also allows multiple components to be consolidated into
a single part, which reduces assembly costs. It will not be long, some in the
industry reckon, before carmakers will offer interior customisation using 3D
printers, too.

Although further development is
needed to speed up additive-manufacturing systems and improve the surface
finish, the technology is already trusted enough to be used in products that
have to withstand high stresses and strains. GE has spent $50m installing a
3D-printing facility at a plant in Auburn, Alabama, to print up to 40,000 fuel
nozzles a year for the new LEAP jet engine it is making in partnership with
Snecma, a French company. The nozzles will be printed in one go, instead of
being assembled from 20 different parts. They are made from a powered “super
alloy” of cobalt, chrome and molybdenum. The finished item will be 25% lighter
and five times more durable than a fuel nozzle made with conventional
processes.

Materials companies are coming up
with more and more specialised ingredients for additive manufacturing. Alcoa, a
leading producer of aluminium, recently said it would supply Airbus with
3D-printed titanium fuselage parts and the pylons used to attach engines to
wings. Alcoa is spending $60m expanding its R&D centre in Pennsylvania to
accelerate the development of advanced 3D-printing materials and processes.

Large 3D printers are also emerging
to make big things. Oak Ridge National Laboratory in Tennessee is working with
a company called Local Motors to print cars, or at least much of their
structure, using a blend of plastic and carbon fibre. The lab has also teamed
up with Skidmore, Owings and Merrill, a firm of architects, to print
substantial sections of buildings. The idea is to develop an additive-building
process that results in no waste.

Some factory bosses have said that
3D printing will never replace mass manufacturing. Perhaps, but it does not
have to in order to transform production processes. Additive-manufacturing
systems are being mashed together with traditional production methods, which
themselves are improving with digital technologies. Even old-fashioned metal
bashing and welding is going high-tech.

Perhaps the surest evidence comes
from China. LITE-ON, a leading contract manufacturer, has just installed a set
of 3D printers in a Guangzhou factory that makes millions of smartphones and
other portable consumer electronics. The printers, made by Optomec, an
Albuquerque-based firm, use a process called Aerosol Jet to focus a mist of
microdroplets into a tightly controlled beam, which can print features as small
as 10 microns (millionths of a metre). LITE-ON is using the machines to print
electronic circuits, such as antennae and sensors, directly into products
instead of making those components separately and assembling them into the
devices either by robot or by hand. When a manufacturing technology arrives in
the workshop of the world, it really is coming of age.